The present invention relates to optical lenses and eyewear including prescription lenses and sunglass lenses, spectacles, lens blanks, sunglasses and safety lenses.
It is known in the prior art to manufacture non-corrective eyeglasses such as sunglasses or protective eyeglasses having wrap-around segments designed to shield the eye from incident light, wind, and foreign objects in the temporal vision field of the wearer. Visible light and light in the UV region may enter the eye from angles as high as 100xc2x0 from the line of sight.
It has not been possible, however, in prior art sunglasses or protective eyeglasses, to provide such spectacles with significant through power, whilst maintaining a cosmetically acceptable appearance. The radius of curvature required to provide an ophthalmic lens including a prescription surface is such that the spectacles would produce a bug-eyed appearance, which would be cosmetically unacceptable.
Today, the vast majority of conventional prescription lenses are relatively flat, single vision, Ostwalt section, miniscus lenses which are glazed like window panes into flat outline spectacle frames.
Applicants have developed certain novel optical lens elements including lens elements with a prescription zone, suitable for use in wrap-around or protective eyewear. The element may also include a peripheral vision zone, with no prismatic jump between the zones. These lens elements are produced by design methods for the prescription zone which include temporally rotating a prescription section about a vertical axis through its optical center and/or decentering the optical axis of the prescription section relative to its geometric axes. These lens elements and design method are described in International Publication No. WO 97/35224 (25 Sep. 1997) to applicants, the entire disclosure of which is hereby incorporated by reference. This application describes the use of close fitting prescriptions shields, visors or dual lens prescription sunglasses by introducing a step change in curvature of the Rx lenses, particularly in the forward visual field of the wearer. However, the technique involves design discontinuities in the optical construction of the lenses, although the visual function is not impaired from the wearer""s viewpoint.
Applicants had developed certain novel lens elements and eyewear characterised by steeply curved surfaces which are approximately spherical and concentric with the centroid of rotation of the eye. These objects are described in detail in U.S. patent application Ser. No. 09/223,006 to Applicants, (xe2x80x9cWide field spherical lenses and single design spectacle thereforxe2x80x9d) filed 30 Dec. 1998, now U.S. Pat. No. 6,124,624, the entire disclosure of which is hereby incorporated by reference. These lenses deviate substantially from conventional, relatively flat lens shapes. However, the overall shape of such lenses may be limited by the spherical reference surfaces employed.
Accordingly, it would be a significant advance in the art if an item of prescription eyewear, for example of the wrap-around type, could be provided which would allow for a wide range of selected styling for both horizontal wrap (around the brows) and vertical shape to maximise the fashion appeal. Furthermore, it would be a further significant advance in the art if the lenses could provide good correction to the full visual field from central to peripheral vision, if desired. Even more preferably, it would be a significant advance if this could be achieved without design features that may create fitting difficulties for a practitioner, or features such as a piano extension which are visible to an observer and diminish the appeal of the product unless it is treated as a tinted or reflective sunglass.
Further, the range of lens shapes in both the horizontal and orthogonal directions is relatively limited in the prior art. The necessity to provide acceptable optical quality has heretofore limited the range of lens element shapes available, particularly with lens elements having significant through power.
It is accordingly an object of the present invention to overcome, or at least alleviate, one or more of the difficulties and deficiencies related to the prior art.
Accordingly in a first aspect of the present invention there is provided an optical lens element including
a first surface; and
a second surface of complementary curvature;
at least one surface exhibiting significant deviation in curvature from a standard optical surface;
the first and second surfaces in combination defining an optical zone exhibiting substantially constant mean through power along at least one meridian.
It will be understood that the optical lens element according to the present invention permits the production of optical lenses with a surface or surfaces of quite radical shape relative to standard ophthalmic lenses, but still providing a lens body for which the mean through power is relatively constant within normal ophthalmic standards. This is despite the fact that the deviating surfaces may exhibit significant optical distortions, e.g. high levels of surface astigmatism over substantial portions of the lens aperture.
Preferably the first and second surfaces are co-varying surfaces such that the optical zone exhibits substantially constant mean through power. More preferably the deviating surface(s) exhibits a substantially smooth change of curvature, at least along a horizontal meridian, across at least a portion of the visual fixation field of the wearer. Thus, the deviating surface(s) may exhibit substantially no visible discontinuity, and more preferably no optical discontinuity. In preferred embodiments the front and/or back surface of the lens element has a surface power which increases in the temporal direction by at least 3.0 D.
In a preferred form, the change in curvature results in a change in sagittal depth of at least approximately 2 mm, preferably at least approximately 4 mm, more preferably at least approximately 9 mm.
In a preferred form, the optical zone of the lens element functions as a prescription zone. More preferably, the lens element has a mean through power between xe2x88x926.0 D and +6.0 D, preferably between xe2x88x924.0 D and +4.0 D.